Traditional hydraulic jacks include a main cylinder, a ram extending from a distal end of the main cylinder, and a pump for driving fluid into a first chamber of the main cylinder, thereby moving the ram from a retracted configuration towards a deployed configuration. In this way, hydraulic jacks are capable of lifting and supporting heavy items. When the jack is no longer required, fluid can be drained from the first chamber of the main cylinder, thereby causing the ram to move towards its retracted configuration.
FIG. 1 shows a cross-section of a portion of a conventional floor jack having a main cylinder 30 positioned within an outer casing 20, thereby defining a reservoir 25 there between. A ram 50 extending into the main chamber 30 includes a piston 52 for dividing an interior area of the main cylinder into first 32 and second 34 chambers. The first chamber 32 extends from the piston to a proximal end of the main cylinder and the second chamber 34 extends from the piston 52 to a distal end of the main cylinder. A shaft 54 of the ram 50 extends from the piston 52 through the second chamber 34 and out the distal end of the main cylinder 30.
A pump 12 is configured to draw fluid from the reservoir 25 and drive the fluid into the first chamber, thereby causing the piston 52 to move away from the proximal end of the main cylinder 30 such that the volume of the first chamber 32 increases as the volume of the second chamber 34 decreases. As the piston moves, fluid from the second chamber 34 travels through a return channel 24 and into the reservoir 25. Because the shaft 54 extends through the second chamber 34, the volume of fluid added to the reservoir 25 is less than the volume of fluid extracted from the reservoir, thereby decreasing pressure within the reservoir 25 and decreasing the efficiency of the pump 12. Consequently, it would be beneficial to have a system for and a method of operating a hydraulic piston while eliminating pressure changes within the reservoir 25.
U.S. Pat. No. 6,318,401 (the '401 patent) and U.S. Pat. No. 7,194,857 (the '857 patent), the entire disclosures of which are incorporated herein by reference, teach ventilation systems that can be utilized to eliminate or further minimize pressure differentials within a reservoir. Specifically, the '401 patent and the '857 patent teach ventilation systems that are configured to engage with a fill hole 22 of the jack, thereby converting the jack from a closed system to an open system.
The outer casing 20 defines a fill hole 22 in fluid communication with the reservoir 25 so as to allow a user to add oil or other fluids to the reservoir 25. A plug 7 is selectively engaged with the fill hole 22, thereby creating a closed system. In this way, fluid is prevented from escaping the reservoir 25 and debris and moisture are prevented from entering the reservoir 25. By replacing the plug 7 with a ventilation system, as taught by the '401 patent and the '857 patent, fluid is no longer prevented from escaping the reservoir 25. In fact, for the ventilation system to work, air within the system must be able to escape from the reservoir 25 into the environment. Unfortunately, oil from within the reservoir 25 can also escape, especially if the jack is stored upside down or on its side. Furthermore, for the ventilation systems taught by the '401 patent and the '857 patent to work, air from the environment must be able to flow into the reservoir 25. Such air from the environment could include debris and/or moisture. Consequently, it would be beneficial to have a system for and a method of eliminating pressure changes within the reservoir 25 while maintaining a closed system.